In the opening of the episode, Tyson explains the nature of the speed of light and how much of the visible universe is made up of light that was emitted billions of years ago. Tyson goes on to describe how contemporary astronomy has used these deep-time investigations to pinpoint the Big Bang event and the universe's age.
Tyson proceeds to describe how the work of Isaac Newton, William Herschel, Michael Faraday, and James Clerk Maxwell contributed to understanding the nature of electromagnetic waves and gravitational force, and how this work led towards Albert Einstein's Theory of Relativity, that the speed of light is a fundamental constant of the universe and gravity can be seen as distortion of the fabric of space-time. Tyson
